Blown mosfet cc lite

I'm sure the two motors did it. I would only use it on single motor applications.

Rod Miller

The stall current for EACH or those motors is 2.5 amps. If you have doubts measure the motor resistance  and divide into 12. 

Pete

I add a PTC for my CC-Lite installations to avoid motor stall issues.  This is after blowing up a beta unit when my K-Line Interurban stalled on a switch.  You can use it with dual motors, but you have to protect it from overload.  I use this Bourns Inc. MF-R075-0-99 1.5A Trip PTC for those installations.

Both motors wired in parallel measure 7 ohms, that should be less than 2 amps at 12v. I hadn't installed any or other options. That was my plan for this mourning. I thought I give it a spin around the layout and just turned the throttle a bit, it moved forward a bit popped and stopped, railsounds didn't quit. I killed the power, removed the shell and found a mosfet had blown apart found no other shorts the other 3 tested good. I tested the current draw of the motors found it the same as before. These motors are horizontal between the wheels and have no fly wheels. Question is the board repairable or is it toast?

,

If the board itself didn't get charred beyond repair, it's a fairly simple matter to replace the FET.

FWIW, the Interurban in my little story was the same type of motors, obviously there's a stall that would seem to generate more current.

Dumb question, will it run in reverse?

I didn't think to try reverse. The 2 outboard fets are marked as fr5305 , how ever the inboard one that's still intact has had id numbers sanded off. Must be a trade secret . I assumed they would be all the same.

It does run in reverse.  radio board and sound module are all good. I did find a small strand of copper wire on the board that most likely caused the short . Never pays to hurry, The fet is a surface mount device,and I no longer have the proper equipment to remove it.  I wonder if ERR would sell the the board by itself.

Contact Ken at ERR, they might replace it if it's a recent board.

Judd posted:

...Question is the board repairable or is it toast?

I'd think the motor drive circuit consists of 2 pairs of FETs (4 total, 2 N-channel, 2 P-channel) in a classic H-bridge configuration.  That's probably why all 4 aren't the same.  If it still works in reverse, there's a reasonable chance simply replacing the $1 FR5305 will bring it back to life.  Working with tiny SMD parts can frustrating...

Stan, I think the inboard FET with the missing numbers is the one that cooked, the LR024Z.  That part is obsolete, it appears that the IRLR024NTRPBF is a replacement, 82 cents/ea at the previous link.

That's even better.  N-channel FETs (like the 024) are usually a bit cheaper than the complementary P-channel FETs.

Yep, for less than $5 shipped, it's worth taking a shot at replacing it.